1. Technical Field
This invention relates to a polymerization grade inorganic dispersion stabilizer and a process for producing resinous particles using the stabilizer. More particularly, the present invention relates to a polymerization grade inorganic dispersion stabilizer capable of improving the stability of suspension polymerization during the course of the polymerization and a process for producing by using the stabilizer such resinous particles as have a narrow particle diameter distribution and, when extracted as dry particles, excel in flowability, show no sign of adhesion or coalition, exhibit a good environmental property and, when required to disperse in a liquid, manifest a veritably excellent redispersibility. This invention further relates to a process for producing resinous particles useful as a negatively or positively charged toner for the development of a static charge image. This invention also relates to a process for producing resinous particles useful as a spacer for a liquid crystal display panels and a liquid crystal display panel. This invention further relates to a process for producing resinous particles useful as a spacer for a touch panel. This invention also relates to a process for producing resinous particles useful as conductive particles.
2. Prior Art
The electrophotographic method comprises forming an electric latent image on a sensitive element formed of such an inorganic electrophotographic material as selenium, zinc oxide, or cadmium sulfide or an organic electroconductive material, developing this latent image with a powdery developer, and transferring the developed image to the surface of paper, for example.
Heretofore, the toner for use in the electrophotographic development has been produced generally by solving and stirring and consequently dispersing a coloring agent and other additives (such as charge regulating agent, offset preventing agent, and slip additive) in a thermoplastic resin, solidifying the resultant dispersion, finely pulverizing the solid mixture, classifying the powder, and separating colored minute particles of a preferred particle diameter.
The method which produces the toner by pulverization as mentioned above, however, has various defects. Firstly, it necessitates numerous steps including a step of producing the resin, a step of mixing the resin with the coloring agent and other additives, a step of pulverizing the resultant solid mixture, and a step of classifying the powder and obtaining minute colored particles of a preferred particle diameter and numerous kinds of devices required therefor. As a natural consequence, the toner produced by this method is expensive. Particularly, the step of classifying the powder to obtain a toner having a particle diameter in the optimum range is an indispensable requirement for the formation of an image which abounds in clarity and suffers the phenomenon of fogging only sparingly. It is, however, problematic in terms of productivity and yield. Secondly, the step of mixing encounters extreme difficulty in uniformly dispersing the coloring agent and other additives in the resin. Hence, the toner produced by this method has the property of triboelectrification varied from one particle to another by the inferior dispersion of the coloring agent, the charge regulating agent, etc. This imperfect stability of the property results in degradation of the resolution. These problems will grow increasingly conspicuous in the future owing to the trend of the toner toward a gradual decrease in particle diameter which constitutes an essential requirement for the improvement of the quality of image. The existing pulverizers have their limits in obtaining a toner of a minute particle diameter. Even when they manage to obtain a toner of a minute particle diameter, they nevertheless entail an increase in the inconsistency of the amount of electrification on account of the inferior dispersion of the coloring agent and the charge regulating agent.
For the purpose of eliminating the various defects which are observed in the toner produced by the method of pulverization, methods for producing the toner by the technique of suspension polymerization have been proposed.
These methods are aimed at synthesizing a toner containing a coloring substance with great dispatch by mixing a polymerizable monomer with a coloring substance such as carbon black and other additives and suspension polymerizing the resultant mixture. These methods are capable of eliminating the defects attendant on the conventional method resorting to pulverization. Since these methods embrace absolutely no step of pulverization and therefore obviate the necessity for improving the embrittleness of the produced toner, the toners they produce are formed of spherical particles and excel in flowability and enjoy uniformity of the triboelectrification.
The liquid crystal display panel comprises two electrode substrates, a spacer for uniformly retaining a cell gap between the substrates, and a liquid crystal (LC). When the display panel of this construction is exposed to a back light, the beams of the back light penetrate through the panel in the portions seating the particles of the spacer and consequently lacking the presence of liquid crystal. This leakage of the back light has the problem of degrading the contrast of image and impairing the quality of display. Particularly the STN-LCE dictates perfect repression of the leakage of the back light through the portions seating the spacer particles because it effects the display in a normally black mode.
As a means to curb the leakage of light through the sites of the spacer particles, the method which comprises coloring the spacer particles has been tried. Among the conventional coloring methods are included those methods which use such coloring agents as dyes and pigments.
The methods for attaining coloration with a dye include a method which comprises suspension polymerizing a monomer and a dye (JP-A-05-301,909 refers), for example. The methods for effecting coloration with a pigment include methods which comprise suspension polymerizing a monomer and a pigment (JP-A-07-2,913 and JP-A-09-25,309), for example.
The transparent touch panel which detects a position pressed with a nib of a pen, for example, and emits the detected position in the form of a signal indicating relevant two-dimensional coordinates is combined with the display screen of a liquid crystal display, EL display, plasma display, CRT (Braun tube), etc. and utilized as a device of easy input in numerous fields.
This transparent touch panel has transparent thin-film electrodes formed one each on the surfaces of the transparent substrates thereof and has these electrodes disposed inside as opposed to each other across an intervening space. For the purpose of separating the electrodes as described above, it has been customary to adopt a method which comprises disposing spherical beads as an insulating spacer between the electrodes which are formed on the substrates.
As a means to produce the resinous particles which are used as the insulating space mentioned above, a method which comprises suspension polymerizing a polymerizable monomer may be cited.
The conventional conductive particles comprise polymer particles and a conductive layer formed on the surface of each of the particles. Generally, the conductive particles are used in the electronics packaging field for the purpose of connecting a pair of electrodes. Specifically, a pair of electrodes having the conductive particles interposed therebetween are pressed against each to establish electric connection between the two electrodes through the medium of the conductive particles.
As a means to produce polymer particles destined to form the basis for the conductive particles mentioned above, a method which resides in suspension polymerizing a polymerizable monomer may be cited.
In the production of resinous particles by such methods of suspension polymerization as are utilized in various applications mentioned above, it is difficult from the technical point of view to effect the polymerization in a system having liquid drops of a monomer composition stably suspended therein without entailing coalition and to obtain by the polymerization minute resinous particles having a uniform particle diameter distribution.
In the suspension polymerization of a polymerizable monomer composition in an aqueous medium, therefore, it has been customary to use a dispersion stabilizer which is capable of preventing polymer particles gradually formed in consequence of the advance of polymerization from succumbing to coalition.
As dispersion stabilizers, such sparingly soluble finely pulverized inorganic compounds as, for example, sparingly soluble salts like BaSO4, CaSO4, MgCO3, BaCO3, CaCO3, and Ca(PO4)2, such inorganic polymers as diatomaceous earth, talc, silicic acid, and clay, powdered metal oxides, or such water-soluble polymers as polyvinyl alcohol, gelatin, and starch have been in popular use.
When a sparingly water-soluble inorganic substance is used, however, in spite of the possibility of this substance acquiring a relatively narrow particle diameter distribution, the amount of this substance to be effectively used is relatively large when it is required to have such a preferred particle diameter as falls in the approximate range of 2-30 xcexcm. Further, owing to the behavior of a surfactant (emulsifier) to be used as an auxiliary dispersion stabilizer, this substance has such a problem relating to the control of particle diameter distribution as the generation of a fine powder owing to the emulsion polymerization which is inevitably entrained. It also calls for an operation of removing the dispersion stabilizer by the washing treatments with an acid and water subsequently to the step of polymerization. If this removal is not thorough, the residue induces the problem of impairing electric properties.
When a water-soluble polymer is used, the particles which are obtained by the suspension polymerization inevitably have an unduly wide particle diameter distribution because they copiously contain particles of minute diameters. In order for the resinous particles to acquire a narrow particle diameter distribution, they require a procedure of performing such complicated works as classification up to several repetitions. Besides, since the dispersion stabilizer deposited on the surface of particles is not easily removed, the particles are at a disadvantage in seriously impairing electric properties and succumbing to such adverse phenomena as cohesion and coalition.
This invention, therefore, has an object of providing a novel inorganic dispersion stabilizer and a process for producing resinous particles using the stabilizer.
This invention has another object of providing a polymerization grade inorganic dispersion stabilizer capable of improving the stability of suspension polymerization during the course of the polymerization and a process for producing by using the stabilizer such resinous particles as have a narrow particle diameter distribution and, when extracted as dry particles, excel in flowability, show no sign of adhesion or coalition, exhibit an excellent environmental property and, when required to disperse in a liquid, manifest a veritably excellent redispersibility.
Further, this invention has an object of providing a process for producing resinous particles which have a narrow particle diameter distribution and consequently permit simplification of the step of classification, enjoy a high yield, and excel in productivity and, when expected to serve as a toner for the development of a static charge image, produce resinous particles useful as a negatively or positively charged toner for static charge image manifesting such outstanding image properties as stabilizing an image, exhibiting good repeatability of fine lines in the image, and precluding the phenomenon of fogging owing to an extremely narrow particle diameter distribution and excellent electric properties.
This invention has another object of providing a process for producing resinous particles which have a narrow particle diameter distribution and consequently permit simplification of the step of classification, enjoy a high yield, and excel in productivity and, when incorporated in a liquid crystal display panel, produce resinous particles useful as a spacer for the liquid crystal display panel manifesting such outstanding properties as precluding the occurrence of an uneven gap, having such strength and hardness as allow easy gap control, suffering only sparing leakage of light through portions encircling the spacer particles, and warranting high reliability and a liquid crystal display panel.
This invention has still another object of providing a process for producing resinous particles which have a narrow particle diameter distribution and permit simplification of the step of classification as a consequence, enjoy a high yield, and excel in productivity and, when incorporated in a touch panel, produce resinous particles useful as a spacer for the touch panel manifesting such outstanding properties as suffering no degradation of the accuracy of detection of the potential of the input, improving the resolution of fine lines of the input, enjoying the linearity of lines of the input, and moreover enabling the electrodes to offer a highly satisfactory insulation and preventing the upper and lower substrates from defective contact or short circuit and a touch panel.
This invention has another object of providing a process for producing resinous particles which have a narrow particle diameter distribution and permit simplification of the step of classification as a consequence, enjoy a high yield, and excel in productivity and, when incorporated in a pair of electrodes destined to be electrically connected, produce resinous particles useful as conductive particles permitting easy retention of a fixed distance between the electrodes and suffering only sparing defective connection.
The objects mentioned above are accomplished by a polymerization grade inorganic dispersion stabilizer, characterized by a process which comprises dispersing a hydrophobic inorganic oxide in an aqueous medium in the presence of a hydrophilic organic compound.
This invention also concerns an inorganic dispersion stabilizer, wherein the hydrophobic inorganic compound is hydrophobic silica and the hydrophilic organic compound is an alcohol.
The objects mentioned above are further accomplished by a process for producing a resinous particles, characterized by dispersing a monomer composition containing a polymerizable monomer in the presence of a polymerization grade inorganic dispersion stabilizer obtained by dispersing the hydrophobic inorganic oxide in an aqueous medium in the presence of the hydrophilic organic compound and polymerizing the resultant dispersion.
This invention also concerns a process for producing the resinous particles, wherein the monomer composition comprises a polymerizable monomer and a coloring agent.
This invention also concerns resinous particles obtained by the process mentioned above.
This invention further concerns a resinous composition which contains the resinous particles mentioned above.
This invention further concerns a toner for the development of a static charge image which contains the resinous particles mentioned above.
This invention further concerns a spacer for use in a liquid crystal display panel which contains the resinous particles mentioned above.
This invention further concerns a liquid crystal display panel which is obtained by using the spacer for use in a liquid crystal display panel mentioned above.
This invention further concerns a spacer for use in a touch panel which contains the resinous particles mentioned above.
This invention also concerns a touch panel which is obtained by using the spacer for use in a touch panel mentioned above.
This invention further concerns conductive particles which comprise the resinous particles mentioned above and a conductive layer formed on the surface of each of the resinous particles.
The present inventors have pursued a diligent study in search of a dispersion stabilizer capable of improving the stability of liquid drops of a polymerizable monomer composition during the aqueous suspension polymerization of the polymerizable monomer thereby producing resinous particles of a narrow particle diameter distribution. They have been consequently ascertained that when a hydrophobic inorganic oxide such as, for example, minute particles of hydrophobic silica is uniformly dispersed in an aqueous medium in the presence of a hydrophilic organic compound such as, for example, an alcohol and dispersing until a prescribed particle diameter, suspending, and suspension polymerizing a polymerizable monomer composition in the resultant aqueous dispersion (now serving as a dispersion stabilizer), the liquid drops during the course of polymerization induce virtually no coalition and resinous particles of an extremely narrow particle distribution are obtained. They have been further ascertained that the resinous particles have a narrow particle diameter distribution and, when extracted as dry particles, excel in flowability, show no sign of adhesion or coalition, and exhibit an excellent environmental property, that the resinous particles, when required to disperse in a liquid, manifest a veritably excellent redispersibility, permit simplification of the step of classification, enjoy a high yield, and excel in productivity, that the resinous particles thus obtained have the electric properties thereof affected only sparingly by the environmental conditions because they have solidified on the surface thereof the hydrophobic inorganic oxide which has been used as one component of the dispersion stability, and that the resinous particles, when expected to serve as a toner for the development of a static charge image, prove to be useful as the material for the toner for static charge image which manifests such outstanding image properties as stabilizing an image, exhibiting good repeatability of fine lines in the image, and precluding the phenomenon of fogging owing to an extremely narrow particle diameter distribution and excellent electric properties because they can be endowed with either positive charge or negative charge by properly selecting the species of a hydrophobic inorganic oxide to be used.
They have been further ascertained that the resinous particles have a narrow particle diameter distribution and consequently permit simplification of the step of classification, enjoy a high yield, and excel in productivity and, when incorporated in a liquid crystal display panel, prove to be useful as a spacer for the liquid crystal display panel manifesting such outstanding properties as precluding the occurrence of an uneven gap, exhibiting such strength and hardness as allow easy gap control, suffering only sparing leakage of light through portions encircling the spacer particles, and warranting high reliability and a liquid crystal display panel and that the produced liquid crystal display panel can be used highly advantageously. This invention has been perfected as a result.
They have been also ascertained that the resinous particles have a narrow particle diameter distribution and permit simplification of the step of classification as a consequence, enjoy a high yield, and excel in productivity and, when incorporated in a touch panel, prove to be useful as a spacer for the touch panel manifesting such outstanding properties as suffering no degradation of the accuracy of detection of the potential of the input, improving the resolution of fine lines of the input, enjoying the linearity of lines of the input, and moreover enabling the electrodes to offer a highly satisfactory insulation and preventing the upper and lower substrates from defective contact or short circuit and a touch panel. This invention has been perfected as a result.
Further, they have been ascertained that the resinous particles have a narrow particle diameter distribution and permit simplification of the step of classification as a consequence, enjoy a high yield, and excel in productivity and, when incorporated in a pair of electrodes destined to be electrically connected, prove to be advantageously useful as conductive particles permitting easy retention of a fixed distance between the electrodes and suffering only sparing defective connection. This invention has been perfected as a result.